Background: Paraproteins often cause factitious biochemical measurements by forming opaque precipitates with the test reagents and interfering with various automated assays. These interferences may be difficult to anticipate as they are intermittent and patient-specific. Increased IgM has been shown to result in the underestimation of uric acid levels and pseudo-hypouricemia; however, there are no reported cases of pseudo-hyperuricemia in the setting of paraproteinemia. Case presentation: We present a case of Waldenström’s Macroglobulinemia (WM), resulting in a marked elevation of the uric acid level in the absence of tumor lysis syndrome (TLS). On evaluation, it was noted that the elevation in the uric acid levels was spurious, potentially due to high IgM levels resulting in increased serum viscosity. Identifying actual and pseudo-abnormal laboratory results is critical to guide further workup and conserve scarce healthcare resources. The absence of other concomitant laboratory abnormalities and clinical symptoms should raise a suspicion of factitious results. In addition to uric acid, many other assays are affected by paraproteinemia, commonly including electrolytes, lipids, glucose, and liver function tests.

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